Room temperature curable coating compositions are widely used as coating materials for on-site application in which cure treatment by heating or the like is difficult, for example, for coating of roofs and walls of outdoor constructions.
Fluororesins, acrylic polyol resins and other hydroxyl-containing resins, which have water repellency, are used as film forming components for these coating materials, and furthermore, hydrophilizing agents such as hydrolysable silicates are sometimes added to enhance a stain proofing property.
However, in the case where hydrolysable silicates are compounded as a hydrophilizing agent, stain proofing property improves, but recoatability is insufficient. For example, exterior walls of constructions are normally coated over a few days. However, when overcoating on the coating film applied on the previous day, the overcoated film is sometimes peeled off. This phenomenon arises particularly significantly in the case where a fluororesin is used as a film forming component and fluoro silicate is used as a hydrophilizing agent. Therefore, the improvement has been desired for solving the problem.
In Patent Document 1, for example, a method for improving recoatability, in which an amine catalyst is used as a curing catalyst to promote the hydrolysis of a hydrophilizing agent and furthermore a silane coupling agent having an isocyanate group at one end thereof is used in combination, is proposed.
In Patent Document 2, the use of a chlorine-substituted alkyl silicate as a hydrophilizing agent is proposed.
Additionally, Patent Document 3 proposes an aqueous coating composition, in which recoatability is improved by compounding an amino-containing silane coupling agent.